Photographic film unit having expandable high volume trap

ABSTRACT

A SELF-DEVELOPING FILM UNIT INCLUDING A PHOTOSENSITIVE SHEET AND A TRANSPARENT SECOND SHEET HELD IN FACE-TO-FACE RELATION WITH RESPECT TO THE PHOTOSENSITIVE SHEET. THE SHEETS ARE BOUND TOGETHER AT THEIR SIDES AND A CONTAINER OR LIQUID PROCESSING COMPOSITION IS SITUATED NEAR A LEADING EDGE OF THE SHEETS. THE SHEETS ARE ADAPTED TO BE MOVED RELATIVE TO PRESSURE-APPLYING ROLLERS, LEADING EDGE FOREMOST, THEREBY SPREADING THE LIQUID PROCESSING COMPOSITION ACROSS THE AREA OF THE PHOTOSENSITIVE SHEET THAT HAS BEEN EXPOSED THROUGH THE TRANSPARENT SHEET. LIQUID PROCESSING COMPOSITION IN EXCESS OF THAT NEEDED TO COMPLETELY COVER THE EXPOSED AREA OF THE PHOTOSENSITIVE SHEET IS COLLECTED IN TRAPPING MEANS NEAR THE TRAILING EDGE OF THE FACE-TO-FACE SHEETS IN A CHAMBER THAT RESPONDS TO AN INCREASE IN HYDRAULIC PRESSURE OF THE EXCESS LIQUID PROCESSING COMPOSITION TO INCREASE ITS VOLUME.

NOV. 23, 1971 J CHEN 3,621,768

PHOTOGRAPHIC FILM UNIT HAVING EXPANDABLE HIGH VOLUME TRAP Filed Aug. 19, 1969 2 ShCC'L5-. hu0r. 1

INVENTOR. RICHARD J CHEN R. J. CHEN Nov. 23, 1971 PHOTOGRAPHIC FILM UNIT HAVING EXPANDABLE HIGH VOLUME TRAP Filed Aug. 19, 1969 2 She0ts-Sheet 2 INVENTOR.

RICHARD J- CHEN United States Patent O 3,621,768 PHOTOGRAPHIC FILM UNIT HAVING EXPANDABLE HIGH VOLUME TRAP Richard J. Chen, Cambridge, Mass., assignor to Polaroid Corporation, Cambridge, Mass. Filed Aug. 19, 1969, Ser. No. 851,291 Int. Cl. G031) 17/50 US. CI. 95-13 12 Claims ABSTRACT OF THE DISCLOSURE A self-developing film unit including a photosensitive sheet and a transparent second sheet held in face-to-face relation with respect to the photosensitive sheet. The sheets are bound together at their sides and a container of liquid processing composition is situated near a leading edge of the sheets. The sheets are adapted to be moved relative to pressure-applying rollers, leading edge foremost, thereby spreading the liquid processing composition across the area of the photosensitive sheet that has been exposed through the transparent sheet. Liquid processing composition in excess of that needed to completely cover the exposed area of the photosensitive sheet is collected in trapping means near the trailing edge of the face-to-face sheets in a chamber that responds to an increase in hydraulic pressure of the excess liquid processing composition to increase its volume.

BACKGROUND OF THE INVENTION (a) Field of the invention This invention relates to photographic apparatus and, more particularly, to a self-developing film unit having expandable means situated at one end thereof to collect liquid processing composition in excess of that needed to fully cover an exposed photosensitive sheet.

The present invention is concerned with photographic film units of the type that include a photosensitive sheet that is exposed through a transparent second sheet held adjacent the photosensitive sheet. A container of liquid processing composition is arranged to be ruptured in an area near the leading edge of the two sheets held in faceto-face relationship so that the liquid processing composition contained therein can be evenly spread between the two sheets over the entire exposed area. Normally, this is done by moving the film unit, leading edge foremost, through and relative to at least two pressure-applying members which cause the liquid processing composition to spread across the exposed area of the photosensitive sheet. A film unit of the type with which the present invention is concerned is more completely described in Ser. No. 622,286 now abandoned, filed on Mar. 10, 1969, and assigned to the same assignee as the present invention. The method of developing is by the diffusion transfer process described more completely in US. Pat. 3,415,644, also assigned to the assignee of the present invention.

Success in developing the latent image contained in the exposed photosensitive sheet depends on the accuracy and completeness of the spreading of the liquid processing composition. In order to insure that the entire exposed area, Without exception, is covered with the composition, the usual technique is to provide in the container near the leading edge of the film unit an amount in ex- Patented Nov. 23, 1971 cess of that needed to cover the exposed area. The exact amount of excess available cannot be calculated to a precise degree because of changes in viscosity, of the processing composition for example, due to temperature variances. It therefore becomes apparent that an excess of liquid processing composition must be provided which will completely cover the exposed photosensitive sheet under the most adverse circumstances, that is, when the temperature is low and the viscosity high. Therefore, under the circumstance where the liquid processing composition is least viscous, a greater amount of excess will be available that must be accommodated after spreading. The low viscosity condition causes the generation of the greatest amount of excess liquid that must be accommodated.

(b) Prior art Various trapping arrangements are utilized in prior art devices for accommodating some of the excess liquid processing composition. However, these arrangements merely provide a greater fixed volume for trapping the fluid. This results in some volume being unused when the extra volume is not needed. Consequently, materials of construction are wasted and the size of the film units is greater than desirable.

In some other prior art film units, a comb-like element is situated near the trailing edge of the film unit and the spaces existing between the teeth of the comb provide the volume to accommodate some excess liquid processing composition. It is obvious that the comb-type traps, as they are called, also represent a fixed volume which can be initially varied during construction when a greater or lesser amount of excess liquid processing composition is expected in a given environment. However, once constructed, these volumes cannot be changed in response to different volumetric needs. Therefore, the non-variable volume traps of the art cannot respond to different amount of excess liquid processing composition to form a trap having a volume that is exactly correct for any given amount of excess. Consequently, the prior art does not provide a complete solution to the problem herein described.

OBJECTS OF THE INVENTION Accordingly, it is an object of the present invention to provide an improved photographic film unit of the type adapted to be processed by moving the film unit relative to pressure-applying means wherein a liquid processing composition is spread by the pressure-applying means in an amount in excess of the amount needed to cover an exposed area of the photosensitive sheet and wherein a liquid trap is provided that has a volumetric capacity varying in accordance with the amount of excess liquid generated.

It is another object of the present invention to provide an improved photographic film unit of the type set forth in the previous object wherein a fixed volume area is provided for excess liquid processing composition with accommodation made for transfer of an amount of liquid processing composition in excess of that amount accommodated by the fixed volume area into an area of variable volume.

It is still another object of the present invention to provide an area in a film unit of the type set forth in the previous objects wherein the amount of liquid processing composition in excess of that amount required to completely cover the exposed area of a photosensitive sheet is first directed to an area in the film unit of relatively fixed volume with an amount in excess of that volume being transferred between pressure-applying means to an area having a volume responding exactly to the amount of the overage of liquid processing composition filling the area of fixed volume.

It is a further object of the present invention to provide a photographic film unit of the type set forth in the previous objects which is readily adapted for use in photographic film units utilized in photographic apparatus already in existence.

SUMMARY OF THE INVENTION Briefly, I accomplish the foregoing objects by providing a photographic film unit of the type adapted to be processed by moving the film unit, leading edge foremost, relative to pressure-applying means which distributes the liquid processing composition from the leading edge of the film unit to the trailing edge thereof, and which includes liquid collecting means adapting the accommodation of different amounts of excess liquid processing composition. The liquid processing composition is normally carried in a container near the leading edge of the film unit and when the film unit is moved between the pressure-applying members, the container is ruptured with the liquid processing composition then being evenly spread across the area of photosensitive sheet, which has been exposed. Depending on the temperature of the film unit at a given time the viscosity of the liquid processing composition varies, resulting in a variable amount of excess liquid processing composition remaining after the photosensitive sheet has been completely covered in the exposed area. The liquid collecting means, or traps, as termed in the art, are carried toward the trailing edge of the film unit and are typified by the spaces between the teeth of a comb-like element. The length of the teeth and the spacing between the teeth determines the amount of fixed volume available for excess liquid processing composition. The present invention resides in the provision of teeth having sufficient length so that when the pressure-applying member is tangential to the surface of the teeth, a path for fiuid flow through the spaces between the teeth is possible from rear to front. Therefore, when excess liquid processing composition is driven into the area provided by the comb trap, an area of expandable volume is always available to accept the excess liquid that the spaces between the teeth of the comb cannot accommodate. In one form, the extra volume is provided by a deflectable wall portion of a depository situated near the trailing edge of the film unit. In another embodiment, the wall portion of the aforementioned depository is folded back upon itself in accordion fashion so that a hydraulic pressure guilt up in the fixed volume portion of the trap will cause the folded portion to expand, thereby providing an area of variable volume. Still another embodiment of the present invention presents an element formed as a rocker-type element which is also a comb-like structure but actually presses the pressure-applying members apart at the time when the space of a fixed volume area is filled, thereby allowing for the transfer of excess liquid processing composition from one side of the comb-like element to the other. On the opposite side of the comb-like element a depository is available to accept and collect the amount of liquid processing composition exceeding the space provided by the area of fixed volume.

BRIEF DESCRIPTION OF DRAWINGS For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings wherein:

FIG. 1 is a perspective view of the film unit of the subject invention;

FIG. 2 is an exploded perspective view of the photo- 4 sensitive and transparent sheet portions of the subject film unit;

FIG. 3 is a sectional view of one embodiment of the subject invention with the pressure-applying rollers shown prior to entering the area of the trap mechanism which has a fixed volume;

FIG. 4 is another illustration of the embodiment of FIG. 3 which shows the pressure-applying rollers directly over the area of fixed volume;

FIG. 5 is a sectional view of another embodiment of the subject invention with a sheet of material being folded back on itself in the direction of the trailing edge of the film unit to provide an area of variable volume;

FIG. 6 is a sectional view of another embodiment of the present invention illustrating a sheet of material folded back on itself in a direction of the leading edge; to pro vide an area of variable volume;

FIG. 7 is a sectional view of another embodiment of the present invention with the pressure-applying rollers engaging the leading edge of a rockable comb-like element; and

FIG. 8 is a sectional view of the embodiment of FIG. 7 showing a progressive position thereof.

FIG. 9 is a perspective view of the comb-like rockable element of the embodiment of FIGS. 7 and 8.

DETAILED DESCRIPTION OF THE INVENTION Referring to FIG. 1, the photographic film unit of the subject invention is illustrated with parts broken away to more clearly illustrate the interior portion of the unit. The film unit is generally designated by the numeral 10 and has a leading edge 12 and a trailing edge 14. Leading edge 12 is the edge of the film unit that first contacts the pressure-applying means of the subject invention as hereinafter described. Near leading edge 12 the liquid processing composition is stored in a plurality of containers or pods 16. Pods 16 are typically formed by a sheet of material 18 folded back on itself and firmly sealed at outside edges 20 and 22. Material 18 is also sealed in areas 24 and 26 so that pods 16 are separate and distinct. Sheet 18 is also sealed in the area defined by edge 28 but this seal is rupturable for reasons which hereinafter become apparent.

Referring to FIG. 2, a transparent sheet 30 and a photosensitive sheet 32 are disposed in face-to-face relationship and are in contact with one another when disposed in film unit 10. A binder 34 is essentially a sheet of material having a window in the center thereof defining the area of photosensitive sheet 32 to be exposed through transparent sheet 30. Binder 34 is wrapped around the side edges 36 and 38 of the face-to-face sheets and is sealed to the exposed surfaces of sheet 30 and 32, respectively. The leading end sections 40 and 42 of the transparent and photosensitive sheets are not sealed together with this unsealed edge facing pods 16 in the area defined by plane 28. This adapts the movement of processing fluid from pods 16 through rupturable area defined by numeral 28 into the space between sheets 30 and 32.

The trailing end sections 41 and 43 terminate in an area in which a comb-like element 44 is disposed. The space between teeth 46 represents an area of fixed volume within the film unit of the subject invention and functions in a manner hereinafter described. This area of fixed volume is generally termed a trap and is adapted to accommodate liquid processing composition in excess of that amount needed to completely cover the exposed area of sheet 32.

The subject film unit is usable in the environment of a camera of the type shown in Ser. No. 655,850 now abandoned, filed July 25, 1967, assigned to the same assignee as the present invention. In this type of camera, film unit 10 is driven between pressure-applying rollers in timed sequence after a desired area of photosensitive sheet 32 is exposed through transparent sheet 30. The latent image in photosensitive sheet 30 is developed by a diffusion transfer process more fully described in US. Pat. No.

3,415,644, also assigned to the same assignee as the present invention. The diffusion process is begun by an amount of liquid processing composition being spread across the exposed area of sheet 32. This liquid processing composition is stored in pods 16 until ready for use.

Leading edge 12 of film unit is driven into pressureapplying rollers of the type shown in FIGS. 3-8 as described in the aforementioned application, Ser. No. 655,850 now abandoned. A hydraulic pressure buildup occurs in pods 16 as the pods pass between the rollers until the pressure ruptures the pods directing fluid toward edge 28. This results in the injection of liquid processing composition into the space between the face-to-face sheets 30 and 32. Continued movement of film unit 10 through the pressure-applying rollers results in the fluid being spread across sheets 30 and 32 in the direction of the trailing end sections 41 and 43, respectively. Depending on the viscosity of the liquid processing composition at a given point in time, an excess of the composition reaches the trailing end sections and enters the spaces between teeth 46 in comb-like element 44 which forms a liquid trap It must be anticipated that at certain times the ambient temperature at which the subject invention is operating is such that an amount of liquid processing composition in excess of that amount capable of being trapped in the spaces between teeth 46 of comb-like element 44 will be encountered. When this occurs, the need for the subject invention arises.

A first embodiment is shown in FIG. 3, where pressureapplying rollers 50 and 52 are rotated in the manner suggested in Ser. No. 655,850 now abandoned. A sheet of material 54 which is actually the rearmost portion of binder 34 is attached across the trailing end section of transparent sheet 30. Transparent sheet 30 is longer than photosensitive sheet 32, resulting in another area of fixed volume 56 being provided near the trailing edge 14 of film :unit 10. Another end of sheet 54 is attached to the opposite outside surface of photosensitive sheet 32 to form an envelope type depository around the trailing end sections of sheets 30 and 32. Comb-like element 44 can be attached to surface of sheet 54 in any well known manner within the depository with the teeth thereof extending into an area adjacent volume 56. Therefore, the liquid collecting means of the subject invention comprises the space between the teeth 46 of element 44, and volume 56, and a chamber that is formed by an expandable portion of material 54 in a manner to be hereinafter described.

In the embodiment shown in FIGS. 3 and 4, a volume 58 is available which is formed by expandable portion 59 of sheet 54. As rollers 50 and 52 assume the position shown in FIG. 3, all of the trapped liquid is in fixed volume 56, in the spaces between teeth 46, and in portion 60 of sheet 64 that is slightly expanded. The volume provided by-the volume 56, portion 60, and the teeth 46 can be too little to accommodate all the excess liquid processing composition when rollers 50 and 52 are positioned as shownin FIG. 4. Consequently, at least the fluid in the volume provided by expanded portion 60 must be transferred to the opposite side of rollers 50 and 52 when these attain the relative position shown in FIG. 4. The fluid is driven through the spaces 46 of comb-like element 44 and this results in the transfer of fluid that cannot be accommodated in fixed volume 56 to be transferred into volume 58. Accordingly, this embodiment of the present invention satisfied the object of providing a fixed volume for some of the excess liquid processing composition and an area of variable volume available on demand for the remaining excess liquid.

Referring to FIG. 5, another embodiment of the present invention is illustrated which is similar to the embodiment of FIGS. 3 and 4. Fixed volume '56 is provided with comblike element 44 having spaced teeth extending adjacent to volume 56. When an amount of liquid in excess of that which can be accommodated in volume 56 is generated,

the liquid falls into the spaces between teeth 46 into an area of variable volume denoted by numeral 62. In this embodiment, a portion of sheet 54 is folded around the trailing edge 14 of the film unit and has a second folded portion 64 that is folded back into itself in the direction of the trailing edge 14 of the film unit. This portion 64 expands in a direction normal to the plane of sheets 30 and 32.

Another embodiment illustrated in FIG. 6 shows the material of sheet 54 folded back over itself in similar fashion to the embodiment of FIG. 5 but with its second folded portion 68 extending in the direction of the leading edge of the film unit. Otherwise, the embodiments of FIGS. 5 and 6 are the same.

Referring to FIGS. 7 to 9, still another embodiment of the invention is illustrated. Sheet 54 is attached to the sheets 30 and 32 in similar fashion to the embodiments of FIGS. 3-6, but with a novel means being provided for the transfer of liquid processing composition exceeding the volumetric capability of chamber 56. More specifically, when the volume 56 is exceeded by an amount of excess liquid processing composition, a shifting of the volume from area 74 into area 76 is accomplished by flowthrough passages disposed in rockable element 78. Element 78 is carried so as to rock on one surface of sheet 32 and is completely surrounded by sheet 54 forming an expandable envelope therearound. That is to say, rockable element 78 is similar to the comb-like structure 44 previously described but allows an amount of liquid processing composition in excess of the capacity of volume 56 to be first carried in area 74 as rollers 50 and 52 advance toward trailing edge 14 and then transfers this amount of excess through the spaces in the comb-like structure 78 into area 76. Sheet 54 is similarly attached to the film unit, that is, similar to the embodiments of FIGS. 36, and has a pair of folded overportions 80 and 82 which form an accordion-like structure near the trailing edge of the film unit. Therefore, as roller-s 50 and 52 assume the position shown in FIG. 7, volume 56 and 74 together as well as the amount of volume in the spaces of the rockable element 78 provide the depository for the excess liquid processing composition. Then, later, as rollers 50 and 52 assume the position shown in FIG. 8, rockable element 78 is shifted into a reverse extreme position which transfers the liquid processing composition from the areas previously described near the trailing edge of the film unit into volume 76 nearer the leading edge of the film unit. Accordingly, a function similar to that performed by the previously described embodiments is performed by a different structure.

To summarize, then, the present invention is concerned with providing for the accommodation of excess liquid processing composition. The amount of excess is predictable only in limited ranges and therefore, it is necessary to provide volumes that can expand or change dimension to accommodate unknown amounts of excess liquid processing composition within wider ranges. One basic necessity of such a structure is that the movement of a film unit relative to pressure-applying rollers generally requires a relatively even spacing to exist between the pressure-applying rollers. That is to say, the rollers exert relatively great pressure on the film unit and as the rollers approach the rear of the film unit, any excess liquid processing composition is normally driven in front of the rollers toward the rear of the film unit. Therefore, as the rollers apporach the trailing edge of the film unit, the volume available to accommodate excess liquid processing composition normally could not exceed the thickness of supported sections defined by the thickness of the sheets supporting or maintaining the rollers in spaced disposition. The essence of the present invention is to overcome this usual volumetric limitation by allowing a shifting of the volume of excess liquid processing composition within the film unit between the rollers when they are relocated at a point forward of the rear edge of the film unit. In

other words, as the rollers approach the trailing edge of the film unit, some type of passages are available to transport excess liquid processing composition within the film unit through the space between the rollers to an area of expandable volume which is then positioned in an area of the film unit already passed by the rollers. Specifically, this volume is illustrated by numeral 58 in the embodiment of FIG. 3, volume 62 in the embodiment of FIGS. and 6, and by volume 76 in the embodiment of FIG. 7. The embodiment of FIG. 7 has the added feature of allowing the pressure-applying rollers 50 and 52 to be pushed further apart due to the tangential contact of the rollers with the rockable element 78 through sheet 54. Accordingly, the objects of the present invention are realized because greater amounts of excess liquid processing composition can be accommodated using the present invention than can be collected using the film units of the prior art.

Since certain changes may be made in the above apparatus without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A photographic film unit of the type adapted to be processed by moving said film unit, leading edge foremost, relative to pressure-applying means for distributing a liquid processing composition from the leading edge toward the trailing edge Within said film unit comprising, in combination:

a photosensitive sheet having a trailing end section and an area to be exposed; a second sheet having a trailing end section; binding means formed of sheet material for holding said photosensitive and second sheets in face-to-face relation so as to allow a thin layer of a liquid processing composition to be spread between said sheets; and

liquid-collecting means carried near the trailing edge of said film unit providing a depository for liquid processing composition in excess of that amount required to cover said area to be exposed, said liquidcollecting means including a portion of said sheet material comprising said binding means, defining a chamber connected to the space between said sheets in which the liquid is spread, said sheet material of said collecting means including at least a section disposed in face-to-face contact with a section of a sheet of said film unit, said sections being movable apart from one another by and in response to hydraulic pressure of the liquid to provide a depository with a section having a volume variable in accordance with the amount of excess processing composition, said section of said depository being located intermediate the leading and trailing edges of said sheets.

2. A photographic film unit according to claim 1 wherein said trailing end section of said second sheet extends beyond said trailing end section of said photosensitive sheet and said variable volume section of said depository is bounded on one side by said trailing end section of said photosensitive sheet.

3. A photographic film unit of the type adapted to be processed by moving said filrn unit, leading edge foremost, relative to pressure-applying means for distributing a liquid processing composition from the leading edge toward the trailing edge within said film unit comprising, in combination:

a photosensitive sheet having a trailing end section and an area to be exposed;

a second sheet having a trailing end section;

means for holding said photosensitive and second sheets in face-to-face relation so as to allow a thin layer of a liquid processing composition to be spread between said sheets;

liquid-collecting means carried near the trailing edge of said film unit providing a depository for liquid processing composition in excess of that amount required to cover said area to be exposed, said liquid-collecting means including a chamber connected to the space between the sheets within which the liquid is spread and expandable by hydraulic pressure of the liquid to provide a volume variable in accordance with the amount of excess processing composition, said chamber providing an area of fixed volume as the depository for excess processing composition up to a predetermined amount; and

means for directing further excess processing composition away from the trailing edge of said film unit.

4. A photographic film unit of the type adapted to be processed by moving said film unit, leading edge foremost, relative to pressure-applying means for distributing a liquid processing composition from the leading edge toward the trailing edge within said film unit comprising, in combination:

a photosensitive sheet having a trailing end section and an area to be exposed;

a second sheet having a trailing end section;

means for holding said photosensitive and second sheets in face-to-face relation so as to allow a thin layer of a liquid processing composition to be spread between said sheets; liquid-collecting means carried near the trailing edge of said film unit providing a depository for liquid processing composition in excess of that amount required to cover said area to be exposed, said liquidcollecting means including a chamber connected to the space between the sheets within which the liquid is spread and expandable by hydraulic pressure of the liquid to provide a volume variable in accordance with the amount of excess processing composition;

an element having flow-through passages situated in depository for transferring from one side of the pressure-applying means to the other side of the pressure-applying means, excess processing composition exceeding a predetermined amount.

5. A photographic film unit of the type adapted to be processed by moving said film unit, leading edge foremost, relative to pressure-applying means for distributing a liquid processing composition from the leading edge toward the trailing edge within said film unit comprising, in combination:

a photosensitive sheet having a trailing end section and an area to be exposed;

a second sheet having a trailing end section;

means for holding said photosensitive and second sheets in face-to-facerelation so as to allow a thin layer of a liquid processing composition to be spread between said sheets; and

liquid-collecting means carried near the trailing edge of said film unit providing a depository for liquid processing composition in excess of that amount required to cover said area to be exposed, said liquidcollecting means including a chamber connected to the space between the sheets within which the liquid is spread and expandable by hydraulic pressure of the liquid to providing a volume variable in accordance with the amount of excess processing composition; said depository having a foldable wall section extending in the direction of the trailing edge of said film unit.

6. A photographic film unit of the type adapted to be processed by moving said film unit, leading edge foremost, relative to pressure-applying means for distributing a liquid processing composition from the leading edge toward the trailing edge within said film unit comprising, in combination:

a photosensitive sheet having a trailing end section and an area to be exposed;

a second sheet having a trailing end section;

means for holding said photosensitive and second sheets in face-to-face relation so as to allow a thin layer of a liquid processing composition to be spread between said sheets; and

liquid-collecting means carried near the trailing edge of said film unit providing a depository for liquid processing composition in excess of that amount required to cover said area to be exposed, said liquid-collecting means including a chamber connected to the space between the sheets within which the liquid is spread and expandable by hydraulic pressure of the liquid to provide a volume variable in accordance with the amount of excess processing composition;

said depository having a foldable wall section extending in the direction of the leading edge of said film unit.

7. A photographic film unit of the type adapted to be processed by moving said film unit, leading edge foremost, relative to pressure-applying means for distributing a liquid processing composition from the leading edge toward the trailing edge within said film unit comprising, in combination:

a photosensitive sheet having a trailing end section and an area to be exposed;

a second sheet having a trailing end section;

means for holding said photosensitive and second sheets in face-to-face relation so as to allow a thin layer of a liquid processing composition to be spread between said sheets; and

liquid-collecting means carried near the trailing edge of said film unit providing a depository for liquid processing composition in excess of that amount required to cover said area to be exposed, said liquid-collecting means including a chamber connected to the space between the sheets within which the liquid is spread and expandable by hydraulic pressure of the liquid to provide a volume variable in accordance with the amount of excess processing composition;

a rocker-shaped element carried on a surface of one of said sheets and surrounded by an expandable envelope which forms said depository, said rockershaped element being rockable toward the leading edge of said film unit as the pressure-applying means approach the trailing edge of said film unit and being rockable toward the trailing edge of said film unit after the film unit has been moved relative to pressureapplying means a further amount.

8. A photographic film unit of the type adapted to be processed by moving said film unit, leading edge foremost, relative to pressure-applying means for distributing a liquid processing composition from the leading edge toward the trailing edge within said film unit comprising, in combination:

a photosensitive sheet having a trailing end section and an area to be exposed;

a second sheet having a trailing end section;

means for holding said photosensitive and second sheets in face-to-face relation so as to allow a thin layer of a liquid processing composition to be spread between said sheets; and

liquid-collecting means carried near the trailing edge of said film unit providing a depository for liquid processing composition in excess of that amount required to cover said area to be exposed, said liquidcollecting means comprising a sheet of material attached to the trailing end section of said second sheet and wrapped around the trailing edges of said second and photosensitive sheets in passing to the opposite side of said film unit against said photosensitive sheet to form a chamber having an expandable Wall portion extending in a direction normal to the plane of said sheets;

a comb-like element encompassed in said chamber so that excess liquid processing composition can move from near the trailing edge of said film unit to an area closer to the leading edge of said film unit when the amount of variable excess liquid processing composition exceeds a predetermined amount.

9. A photographic film unit according to claim 3 wherein said last-mentioned means includes a comb-like element.

10. A photographic film unit according to claim 5 wherein said liquid-collecting means includes a sheet of material attached to one surface of said second sheet and is folded around the trailing edge of said film unit and attached to the surface of said photosensitive sheet, said sheet of material having a portion folded back into itself in the direction of the trailing edge of said film unit.

11. A photographic film unit according to claim 6 wherein said liquid-collecting means includes a sheet of material attached to one surface of said second sheet and folded around the trailing edge of said film unit and attached to the surface of said photosensitive sheet, said sheet of material having a portion folded back into itself in the direction of the leading edge of said film unit.

12. A photographic film unit according to claim 7 wherein said rockable element is comb-like in shape and rockable on said photosensitive sheet first allowing a depository near the trailing edge of said film unit to be filled with excess liquid processing composition while later allowing an amount exceeding the capacity of said depository to be transferred through said rockable element into the direction of the leading edge of said film unit into a compartment formed by a folded sheet of material attached at one end to a surface of said second sheet and at another end to a surface of said photosensitive sheet with folds therein extending both toward the trailing and leading edges of said film unit.

References Cited UNITED STATES PATENTS 2,627,460 2/ 1953 Land 9676 X 2,686,716 8/1954 Land 9676 X Re. 25,167 5/1962 Booth et al -13 3,320,065 5/1967 Campbell 9676 3,352,674 11/1967 Harvey 9676 X SAMUEL S. MATTHEWS, Primary Examiner R. L. MOSES, Assistant Examiner US. Cl. X.R. 

